I am restoring a 1987 K100 RT and have a problem diagnosing the wiring system. I have researched every electrical diagram I can find linked from this forum plus several othe sources, but I have found none that include the alarm/antitheft unit that appears to be an original component in my machine (very well incorporated into the bike's wiring harness). It is marked 'TUV' and has a seat button, plus a keyed switch that is in the relay box left side (and I didn't get a key from the seller as the bike has been sitting for many years). I am getting no voltage to the starter button on the right handlebar, and thereby no activation at the starter relay. Indicator lights on the instrument panel are nonfunctional as well. By jumping the two wires to the alarm switch it does activate the imtermittent horns, but I can't seem to logic the unit's full functionality so I can debug the wiring.

Since I am restoring the bike as an educational venture, I'd like to know how the unit should operate with the 5 wires going to the alarm unit so I can verify it's functionality, or at least how to remove it fully from my bike's system and rewire.

Any help?

Well I cannot be a great help as I don't know anything about the alarm.
Why don't you disconnect it to get the bike running first? You can play with it later...
The plug for the alarm is in the relay box. You can see which plug it is here:

Bert

Update: I've been working on the bike today and have got the alarm system figured out. Thanks for the diagram, your diagrams and schematics have been my primary source for checking out my wiring harness.

Everything functions as it should (for the most part) except the gear indicator. I've checked and cleaned the connector to the right of the batteryto no avail. Any diagrams or direction on how signals are sent to the instrument cluster thru the 4 wires so I can see if it is the sending unit or the instrument cluster?

Check this link: testing the gear indicator switch
Most of the time the contacts are corroded and opening the switch to clean it is required.
Check K100 rebuilt page. I explain how to open the switch and clean it.

Bert]

Hi Loner,
That sounds like the standard BMW bike alarm which is shown on the BMW circuit diagram I have seen. I will look for it tomorrow, sorry I cannot do that right now as I am off to Lodge with a neighbour who is here on holiday and he wanted to visit a Lodge tonight.
Regards,
K-BIKE

Hi Loner,
The original alarm box has a key switch which shorts across between pin 5 and pin 31 on the alarm control box to set the system, wires brown and brown/black.

Pin 31 on the control box also connects to pin 31 on the temperature relay, wire brown.

Pin 30 on the control box goes to power via fuse 5 wires red/yellow.

Pin H on the control box goes to the horn relay wires green/grey.

The plug under the seat for the alarm plugs straight in to the loom for the alarm.

It is a pretty basic alarm! I don't know this for sure but the connection to the temperature relay says to me (huge SWAG coming up) that the start is disabled by fooling the temperature relay that the bike is over temperature.
Regards,
K-BIKE

I would agree with K-Bike about the alarm and the temperature relay.
I had seen on other forums that the a K bike will not start if the water temperature is too high but never tried it to prove it.
If this theory is right, this is a cheap way to make a protection system.
A simple hidden switch to ground the water temperature sensor should make an efficient engine immobilizer.

Thanks to both of you - the wealth of information that is disseminated on this forum is astounding. I just hope I can contribute some worthy information in the future.

You're welcome loner.

it is true that we have a lot of information, and this is the result of research and people sharing their experience. Soon we will be able to publish a K100 encyclopedia.

Hi Loner,
We are one big family and all family members contribute what they can to the family knowledge pool. Everyone has their own area of expertise and the great thing about this family is anyone can ask any question and someone somewhere round the world will answer it.
Regards,
K-BIKE

I started reading this cos I thought
"alarm? I aint got no alarm, how come he's got an alarm?"
then saw the relay diagram and thought " Oooh! useful" and grabbed that
then learnt about the temp sensor trick
Didnt know that, very handy to know

Great here aint it?
Lotsa good stuff

does BMW provides wireless control together ???

greecek100rt wrote:does BMW provides wireless control together ???

AFAIK that was never an option on the K100 models.
It was/is available for the K1100 models, which have quite different wiring system.

Inge K.

Inge K. wrote:

greecek100rt wrote:does BMW provides wireless control together ???

AFAIK that was never an option on the K100 models.
It was/is available for the K1100 models, which have quite different wiring system.

Inge K.

THANK YOU

You might get one that is meant for a K11 to function on a K100,
but it wouldn`t be just plug and play.

Inge K.

As soon as i will disassembly the alarm system from my RT i will show you pics for further investigation. But it looks very simple system.

BMW K100 alarm system wiring diagramm
even if probs solved:

K100 Alarm Diagram

With typical Teutonic efficiency in design the BMW alarm prevents a start but does not kill the bike when running. Many after-market alarms kill the ignition and or the fuel injection signals. Now given that the average after-market alarm is very poor quality in a very agressive environment a failure is inevitable sometime in the future, just hope it does not happen when overtaking at 100 on a motorway

Best not to interrupt either fuel or ignition with any device that can fail when driving. Top marks to BMW for their original design.
Regards,
K-BIKE

i hope you can see now the pics sorry for my mistake before

pls check the links before posting (preview)

none of them works

K-BIKE wrote:Hi Loner,
The original alarm box has a key switch which shorts across between pin 5 and pin 31 on the alarm control box to set the system, wires brown and brown/black.

Pin 31 on the control box also connects to pin 31 on the temperature relay, wire brown.

Pin 30 on the control box goes to power via fuse 5 wires red/yellow.

Pin H on the control box goes to the horn relay wires green/grey.

The plug under the seat for the alarm plugs straight in to the loom for the alarm.

It is a pretty basic alarm! I don't know this for sure but the connection to the temperature relay says to me (huge SWAG coming up) that the start is disabled by fooling the temperature relay that the bike is over temperature.
Regards,
K-BIKE

I have a similar issue, but my bike seems completely different from the diagrams that I have seen.  The connector to the alarm unit has 5 pins, not 4 like I have seen in diagrams in my Clymer manual.  The connector housing pins are labeled 30, 71a, 31, 85c, and 15.  I have ordered a replacement 4.8 volt battery for it, but still want to troubleshoot the unit  and the wiring in the bike.  This all started when I replaced my 12 volt battery after the bike had sat for a long period of time and now the horn blows when I turn the ignition switch on.  The alarm unit relay is being energized, but I don't know if its caused by something internal to the alarm unit or external in the bike wiring.  The 4.8 volt battery has caused some corrosion within the alarm unit itself and I suspicion an internal alarm unit problem, since all was well when it was parked.  My operator's manual is the original that came with the bike and there is no mention of an alarm unit and the alarm unit is not in the wiring diagram of the manual.

geharper wrote:
I have a similar issue, but my bike seems completely different from the diagrams that I have seen.  The connector to the alarm unit has 5 pins, not 4 like I have seen in diagrams in my Clymer manual.

At this point, posting an image of your bike's unit, connectors and wiring would be appropriate.

Does this post and others following it help?
https://www.motobrick.com/index.php/topic,9008.msg71239.html#msg71239

geharper wrote:
I have a similar issue, but my bike seems completely different from the diagrams that I have seen.  The connector to the alarm unit has 5 pins, not 4 like I have seen in diagrams in my Clymer manual.  The connector housing pins are labeled 30, 71a, 31, 85c, and 15.

The wiring diagram which is 404 in post #17 you now can find HERE
which I'll guess is what you searching for.
A difference from yours is the terminal designations where those
ones on the diagram is of a older version.........71a=H, 85c=S.

Inge K. wrote:

geharper wrote:
I have a similar issue, but my bike seems completely different from the diagrams that I have seen.  The connector to the alarm unit has 5 pins, not 4 like I have seen in diagrams in my Clymer manual.  The connector housing pins are labeled 30, 71a, 31, 85c, and 15.

The wiring diagram which is 404 in post #17 you now can find HERE
which I'll guess is what you searching for.
A difference from yours is the terminal designations where those
ones on the diagram is of a older version.........71a=H, 85c=S.

Thank you Inge K., this will be very helpful.

So does simply unplugging the connector for the anti theft unit in the relay box just disable the alarm system and allow normal running? I
E. Simply by passing it..

Foxxys wrote:So does simply unplugging the connector for the anti theft unit in the relay box just disable the alarm system and allow normal running?

In this post—https://www.k100-forum.com/t14148-turns-over-then-backfires#166383—it seems you have written that you already tried unplugging the connector and describe the results. Unplugging the connector didn't disable its effect. Is that correct?

If the alarm's effects on the moto are to be eliminated, it must be bypassed or the moto's wiring restored to its original routing before disconnecting and removing it. Bypassing the alarm's wiring is described in this post and links in that thread—https://www.k100-forum.com/t13784p50-a-modern-k-bike#165929—but there might be a couple of different styles of alarms that interfere with starting by different methods.

Whether the alarm is causing your moto's present problem is unknown.